1. Field of the Invention
This invention relates to an electrode for damaging tissue within a patient's body and more particularly to an electrode which damages tissue by delivering a conductive fluid and radio frequency energy to a selected site within a patient's body.
2. Description of Related Art
It is often desirable to damage tissue at selected sites within the body without open surgery. For instance, when treating malignant tumors, abscesses, or infected tissue, a physician wants to destroy the tissue within a patient's body. In open surgery the physician opens the patient and attempts to physically remove the targeted tissues. However, open surgery can cause additional complications such as infection. Thus, several closed surgery techniques have been developed for damaging tissue. For instance, radiating the patient from an external source has been tried. Unfortunately, since the source is external, the radiation can not be sufficiently localized to the targeted tissue, thus, healthy tissue which has not been targeted can be damaged.
A recent technique which provides more localized treatment of the target tissue involves introducing a radio frequency (RF) electrode into the target tissue. In this technique, the physician places the electrode within the target tissue using techniques such as fluoroscopy, ultrasound, or manual palpitation. The physician then applies RF energy to the electrode which heats the tissue surrounding the electrode. Tissue is generally sensitive to heat such that high levels of heat or simply sustained heat can damage or destroy it. Once the physician has applied a desired amount of energy, the treatment is complete and the physician withdraws the electrode.
There are several difficulties with this technique. For instance, tissue adjacent to the electrode begins to desiccate very quickly, particularly when there is a high current density on the surface of the electrode. Once the tissue desiccates, the ability of that tissue to conduct RF energy is reduced. Thus, once the tissue becomes desiccated around the electrode, the ability of the electrode to treat tissue remote from the surface of the electrode is diminished. As a result, this technique is most effective for treating tissues which are closest to the surface of the electrode.
Another difficulty can arise when the physician must perform successive treatments. Often, the first treatment does not completely destroy the target tissue and additional treatments are required. To perform additional treatments, the physician must attempt to reinsert the electrode into the same target tissue. To do this, the physician often wants to puncture the same point on the patient's skin. However, scar tissue is often present from the previous surgery, thus, the physician usually does not want to puncture the same point again and must puncture the skin in a new location. This means the electrode will not approach the target site from the same angle and may result in imprecise placement of the electrode.
For the above reasons, there is a need for a method and device which can locally damage target tissue without open surgery. The method and device should allow the physician to easily treat tissue remote from the surface of the electrode. Further, the method and device should allow a physician to easily treat the same area of the target site each time a treatment is performed.